Non-volatile resistive memory devices are an important element of integrated circuit devices due to their ability to store data absent a power supply. Resistive memory cells store data by switching between different resistance states. For example, for binary data storage, a high-resistance state of the resistive memory cell may be read as logical “1,” while a low-resistance state of the resistive memory cell may be read as logical “0,” or vice versa. Switching between resistance states may be achieved by applying different physical signals (e.g., voltage, current) across the resistive memory cell to form, at least partially remove, or repair conductive filaments in a resistive memory element therein. Forming the conductive filaments can decrease the resistance of the memory cell, removing the conductive filaments can increase the resistance of the memory cell, and repairing the conductive filaments can decrease the resistance of the memory cell once again. Conventionally, the initial formation of the conductive filaments is referred to as “forming,” the at least partial removal of the conductive filaments is referred to as “resetting,” and the repair of the conductive filaments is referred to as “setting.”
One example of a resistive memory cell is a programmable metallization cell (PMC), also referred to as a conductive-bridging random access memory (conductive-bridging RAM) cell. In a conventional PMC, the resistive memory element includes an inert electrode, an active electrode (also referred to as an “ion reservoir material”), and an active material (also referred to as a “switchable resistance material”) between the inert electrode and the active electrode. A conductive filament extending through the active material can be formed by applying a physical signal (e.g., voltage) across the electrodes to effectuate the drift (e.g., diffusion) of metal cations (e.g., copper cations, silver cations) from the active electrode, through the active material, and to the inert electrode, where the metal cations are electro-chemically reduced. The conductive filament may be removed by applying a different physical signal (e.g., a voltage with reversed polarity) across the electrodes, or may remain in place indefinitely without needing to be electrically refreshed or rewritten.
Many conventional PMCs also include a buffer material disposed between the active electrode and the active material. The buffer material can facilitate the controlled diffusion of metal cations from the active electrode into the active material, and can also limit or prevent undesirable migration of one or more material constituents from the active material into the active electrode (and/or vice versa). Conventional buffer materials are typically formed of and include a substantially amorphous material, such as a substantially amorphous chalcogenide material (e.g., aluminum telluride). Unfortunately, the material properties of conventional buffer materials can result in undesirable memory cell performance, reliability, and/or durability. For example, the amorphous materials of many conventional buffer materials have relatively low crystallization temperatures, and may readily switch from an amorphous state to a crystalline and/or semi-crystalline state during normal use and operation of a memory cell. Such switching of states can result in memory cell damage due to phase separation of different memory cell components and/or in poor memory cell endurance. In addition, the relatively low thermal stability of conventional buffer materials can negatively impact the overall thermal stability of a memory cell, limiting one or more of processing (e.g., fabrication) temperatures and operating temperatures of the memory cell. In addition, the material properties of many conventional buffer materials can result in the inconsistent (e.g., variable, random) formation of a very limited number of conductive filaments. If one or more of the very limited number of conductive filaments fails (e.g., is undesirably disrupted or destroyed), the performance and/or reliability of the memory cell can be undesirably diminished or destroyed.
A need, therefore, remains for resistive memory elements, such as resistive memory elements for PMCs, including new buffer materials that resolve one or more of the foregoing disadvantages of conventional buffer materials, as well as for memory cells, memory devices, and electronic systems including the resistive memory elements, and simple, efficient methods of forming the resistive memory elements.